• Title/Summary/Keyword: effective diffusion

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Fabrication of coated conductor stacked multi-filamentary wire (적층형 초전도 다심 선재 제조)

  • Yun, K.S.;Ha, H.S.;Oh, S.S.;Moon, S.H.;Kim, C.J.
    • Progress in Superconductivity and Cryogenics
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    • v.14 no.1
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    • pp.4-7
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    • 2012
  • Coated conductors have been developed to increase piece length and critical current for electric power applications. Otherwise, Many efforts were carried out to reduce AC loss of coated conductor for AC applications. Twisting and cabling processes are effective to reduce AC loss but, these processes can not be applied for tape shaped coated conductor. It is inevitable to have thin rectangular shape because coated conductor is fabricated by thin film deposition process on metal substrate. In this study, round shape superconducting wire was first fabricated using coated conductors. First of all, Ag coated conductor was used. coated conductor was slitted to several wires with narrow width below 1mm. 12ea slitted wires were parallel stacked on top of another until making up the square cross-section. The bundle of coated conductors was heat treated to stick on each other by diffusion bonding and then copper plated to make round shape wire. Critical current of round wire was measured 185A at 77K, self field.

Investigation of Soot Formation in a D.I. Diesel Engine by Using Laser Induced Scattering and Laser Induced Incandescence

  • Lee, Ki-Hyung;Chung, Jae-Woo;Kim, Byung-Soo;Kim, Sang-Kwon
    • Journal of Mechanical Science and Technology
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    • v.18 no.7
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    • pp.1169-1176
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    • 2004
  • Soot has a great effect on the formation of PM (Particulate Matter) in D.I. (Direct Injection) Diesel engines. Soot in diesel flame is formed by incomplete combustion when the fuel atomization and mixture formation were poor. Therefore, the understanding of soot formation in a D.I. diesel engine is mandatory to reduce PM in exhaust gas. To investigate soot formation in diesel combustion, various measurements have been performed with laser diagnostics. In this study, the relative soot diameter and the relative number density in a DJ. engine was measured by using LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence) methods simultaneously which are planar imaging techniques. And a visualization D.I. diesel engine was used to introduce a laser beam into the combustion chamber and investigate the diffusion flame characteristics. To find the optimal condition that reduces soot formation in diesel combustion, various injection timing and the swirl flow in the cylinder using the SCV (Swirl Control Valve) were applied. From this experiment, the effects of injection timing and swirl on soot formation were established. Effective reduction of soot formation is possible through the control of these two factors.

Numerical study on PEM fuel cell performance with variation of GDL permeability and channel geometry (기체확산층의 유동투과율과 채널 형상 변화에 따른 고분자 전해질 연료전지 성능변화 수치연구)

  • Koh, Soo-Gon;Sohn, Sang-Ho;Nam, Jin-Hyun;Kim, Charn-Jung
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.3114-3119
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    • 2008
  • Relatively high convective flow exists in the under-rib regions of a gas diffusion layer (GDL) when serpentine flow fields are employed in a PEMFC. This under-rib convection is believed to be favorable for the performance of PEMFCs, by enabling more effective use of catalysts in the under-rib regions. From the fact that the under-rib convection in a GDL is directly proportional to the permeability of the GDL, computational fluid dynamics (CFD) simulations were performed to discover the relationship between the GDL permeability and the PEMFC performance. Single-, triple-, and quintuple-path parallel serpentine flow fields for $9\;cm^2$ active cell area were considered while changing the GDL permeability from $1{\times}10^{-12}$ to $5{\times}10^{-11}m^2$. The results showed that higher GDL permeability generally resulted in better performance of PEMFCs, but the degree of performance enhancement became smaller as the parallel path number increased. The effects of the permeability on the local variables were also discussed.

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Numerical Simulation of the Odor Spreading in a Factory (공장에서 퍼지는 냄새에 관한 수치계산적 연구)

  • Vincent, Lijo;Song, Eun-Hwa;Nam, Hyun-Kyu;Shin, Choon-Sik;Kim, Heuy-Dong
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2540-2543
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    • 2008
  • Liquid crystal displays (LCD's) are continuously coated with some chemicals in the clean room of a factory. Spreading of these chemicals is causing serious problems both in controlling clean room quality as well as to the workers inside the factory. It is required to alleviate or properly control the offensive odor which is mainly composed of propylene glycol mono ethyl acetate, novolak resin and photo active compound. The control strategy employed is to bleed the offensive odor gas out the clean room. A full scale 3D CFD model was created with anisotropic porous media, chemical species transport with no volumetric reaction, and thermal diffusion with propane gas (tracer gas) to simulate the odor spreading. A segregated implicit solver with standard k-$\varepsilon$ model is employed. The detailed CFD analysis made it possible to develop an effective method of ventilating the coater room and optimizing their capacities.

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A Technology for Water Pollution Diffusion Prevention based on Web Map

  • Shin, Jin Seob
    • Journal of the Korea Society of Computer and Information
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    • v.22 no.11
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    • pp.65-71
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    • 2017
  • An integrated water environment management system is necessary in improving water quality, properly allocating water resources, and supporting socio-economic development. Specifically, water quality management system using web map can be an efficient approach to accomplish this system. This paper aims to construct a dynamic water quality management system to reflect a water environment management system which includes three sub-models with consideration of their interrelationships (a socio-economic model based on dynamic Input-Output model, a water resources cycle model, and a water pollutants flow model). Based on simulation, the model can precisely estimate trends of water utilization, water quality, and economic development under certain management targets, and propose an optimal plan. This study utilized the model to analyze the potential of using reclaimed water to accomplish local water environment management and sustainable development plan while exploring the applicable approaches. This study indicates that the constructed water environment management system can be effective and easily adopted to assess water resources and environment while improving the trade-off between economic and environment development, as well as formulate regional development plan.

Intrinsic and Extrinsic Factors Impacting Individuals' Cyber Ethics Awareness and Behavior Intention (사이버윤리 준수인식과 행동의도에 영향을 미치는 사용자의 내·외적요인)

  • Kim, Sanghyun;Park, Hyunsun
    • The Journal of Information Systems
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    • v.23 no.1
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    • pp.111-138
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    • 2014
  • As the Internet is widely used worldwide, Cyber world has become a part of daily life. On the other hand, the adverse effects of Internet, such as abusive comments, illegal harmful contents, rumor diffusion, infringement on a right have emerged with the increase. Researchers recognized the important of cyber ethics as an effective means of coping with the adverse effects on Internet. But, Little empirical research has been related to cyber ethics in management information systems. Thus, the purpose of this research is to identify multidimensional motivation factors that cyber ethics awareness and compliance behavior Intention. For this, this study investigated the factors that might influence Internet users to compliance cyber ethics. Using university students as a sample, one hundred and ninety six are collected for further analysis. The results of this study are as follows; First, self-esteem, Moral Obligation, self-control, cyber ethics education and Social Influence are significantly related to cyber ethics awareness, while punishment is not significantly related. Second, cyber ethics awareness have a positive effect on cyber ethics compliance behavior Intention. Third, the moderating effect of ego strength is also significant. This study is significant in that it established a behavior model to understand the compliance of cyber ethics with internet user in Korea.

Development of In-Core Fuel Management Scoping Tools for PWR (가압경수로의 노심내 핵연료관리용 탐색도구의 개발)

  • Kim, Chang-Hyo;Kim, Teak-Kyum
    • Nuclear Engineering and Technology
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    • v.25 no.1
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    • pp.20-27
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    • 1993
  • This paper concerns with developing a simplified in-core fuel management scoping tool for PWR. For this purpose the point reactivity model is put into a fuel cycling decision code, FCYPRM. Modified Borresen's coarse-mesh diffusion theory and nodal expansion method are utilized to form a spatial neutron analysis code, CMSNAP. Numerical experiments are per- formed to determine a set of empirical shuffling rules for working out an automated fuel loading pattern search code, ALPS. The numerical examples are presented for verifying effectiveness and applicability of individual codes. By structuring and applying three codes for reload core design problem of a PWR, it is demonstrated that these codes provide an effective in-core fuel management scoping tool for PWR.

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Microencapsulation of Isoprinosine with Ethylcellulose

  • Kim, Chong-Kook;Hwang, Sung-Joo
    • Archives of Pharmacal Research
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    • v.14 no.4
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    • pp.298-304
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    • 1991
  • Isoprinosine, an antiviral agent with a bitter taste, has been clinically used up to a maximum of 4 g daily in 4-8 doses. In this investigation, isoprinosine was microencapsulated with ethylcellulose 22 cps, 50 cps and 100 cps by means of polymer deposition from cyclohexane through temperature change. Complete removal of cyclohexane from the microcapsules was necessary, since ethylcellulose-coated microcapsules obtained from cyclohexane medium were heavily solvated with cyclohexane and formed lumps even after drying. The displacement of cyclohexane by n-hexane during isolation of microcapsules (Method III) or the freezing of the anal-washed microcapsules before drying (Mothod II) provided the dried products which were more discrete microcapsules than those which were simply dried in the air overnight (Method I). Method III was especially the most effective procedure in preparing finer and more discrete microcapsules. The drug-release from microcapsules was influenced by the ratio of core to wall, the viscosity grade of ethylcellulose and the overall microcapsule size. The release rate was adequately fitted to both the first-order and the diffusion-controlled processes. It is therefore possible to design the release-controlled microcapsules with ethylcellulose of different viscosity along with various core to wall ratio.

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Antibacterial and Nitric Oxide Production Inhibitory Activities of Prunus sargentii Branches Extract and Its Fractions against Pathogens of Acne (산벚나무 가지 추출물 및 용매 분획물의 Nitric Oxide 생성 억제 효과와 여드름 원인균에 대한 항균활성)

  • Yang, Sun A;Pyo, Byoung Sik;Kim, Sun Min
    • Korean Journal of Medicinal Crop Science
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    • v.24 no.2
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    • pp.129-135
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    • 2016
  • Background: In this study, we investigated the antibacterial and nitric oxide (NO) production inhibitory activities of 75% ethanol extract of Prunus sargentii branches and its fractions against acne pathogens. Methods and Results: The antibacterial activity against acne causing pathogens was determined using the disc diffusion assay. The ethyl acetate fraction showed higher activities against Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis than those shown by other fractions. In the DPPH radical and NO scavenging assays, the butanol fraction showed strong DPPH radical and NO scavenging abilities. These activities were related to the total polyphenol and flavonoid contents of butanol fraction. On the other hand, the chloroform and ethyl acetate fractions exhibited the highest NO production inhibitory activity in Lipopolysaccharide (LPS)-stimulated Raw 264.7 cells compared to those exhibited by other fractions. Conclusions: The extract and its ethyl acetate fraction from the branches of P. sargentii exhibited antibacterial activity and could be used as functional materials in antimicrobial related fields. Moreover, the chloroform and ethyl acetate fractions are potential antiinflammatory agents and butanol fraction acts as an effective radical scavenger.

Antioxidative and Antibacterial Activity and Tyrosinase Inhibitory Activity of the Extract and Fractions from Taraxacum coreanum Nakai (흰민들레 에탄올 추출물 및 분획물의 항산화 및 항균활성과 Tyrosinase 저해활성)

  • Im, Do-Youn;Lee, Kyoung-In
    • Korean Journal of Medicinal Crop Science
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    • v.19 no.4
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    • pp.238-245
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    • 2011
  • In this study, we investigated antioxidative activity, antibacterial activity against pathogenic strains including methicillin resistant Staphylococcus aureus (MRSA), and tyrosinase inhibitory activity in 75% ethanol extract of Taraxacum coreanum and its fractions. The total polyphenol and flavonoid contents of the extract were 238.59mg/g and 33.18mg/g and the total polyphenol and flavonoid contents of the ethyl acetate fraction were 427.81mg/g and 148.90mg/g as the highest content of fractions. In DPPH radical scavenging ability, $SC_{50}$ values of the ethyl acetate and butanol fraction were 38.40${\mu}g/ml$ and 82.28 ${\mu}g/ml$, respectively. In antibacterial activity by the disc diffusion assay against S. aureus, S. epidermidis and MRSA, the ethyl acetate fraction showed stronger antibacterial activity than other fractions and the extract. Especially, the ethyl acetate fraction was exhibited effective antibacterial activity against MRSA. In the cytotoxicity measurement by MTT assay, the extract and fractions were exhibited Raw 264.7 cell viabilities of 96.32~143.21% as nontoxic result in concentration of 5~100 ${\mu}g/ml$. As a result, the ethyl acetate fraction of the 75% ethanol extract from T. coreanum could be applicable to functional materials for related fields.